Unfortunately herbicides are the only thing that I have seen to be really
effective. You need to use glyphosate that is labled for wet areas, and
you have to hit it year after year to "knock it back". Like most of these
exotics, unfortunately, whenever you stop controling it, it just starts
slowly coming back over time. Good Luck, and if you find anything else
that really controls it let us know on the east coast.